Process for obtaining polyamide yarns with better output efficiency

Abstract

An improved output efficient polyamide-based preoriented yarn spun at a speed of at least 4000 m/min and obtained by introducing, before the spinning, of a quantity of 0.05 to 1% by weight of pyrogenic silica of particle size of between 5 and 15 nm into the molten polymer in the form of dispersion in a master mix of the same polyamide as that intended to be processed, the filaments after spinning being then cooled by means of a gas stream at room temperature and then sized and wound at a speed of between 4200 and 5800 m/min. The preoriented yarns thus prepared exhibit a delay in the orientation and are obtained with a gain in output efficiency of at least 10%, generally at least 15%.

We claim: 
     
       1. Undrawn preoriented polyamide yarns containing from 0.05 to 1% by weight of uniformly distributed pyrogenic silica of particle size of between 5 and 15 nm, said yarns exhibiting a delay in orientation. 
     
     
       2. Undrawn preoriented polyamide yarns containing from 0.5 to 1% by weight of pyrogenic silica of particle size of between 5 and 15 nm, said yarns exhibiting a delay in orientation, said yarn being obtained by introducing a quantity of 0.05 to 1% by weight of pyrogenic silica of particle size of between 5 and 15 nm into molten polyamide polymer in the form of a dispersion in a master mix of said same polyamide, spinning said polymer at a speed of at least 4000 m/min into filaments, cooling said filaments by means of a gas stream at room temperature and then sizing and winding said filaments at a speed of between 4200 and 5800 m/min. 
     
     
       3. The undrawn preoriented polyamide yarns according to claim 1, wherein the pyrogenic silica particles are in the form of aggregates, said pyrogenic silica particles having a mean interparticular distance therebetween of between 0.2 and 0.7 μm, said aggregates having a maximum distance between two silica aggregates of ≦3 μm. 
     
     
       4. The undrawn preoriented polyamide yarns according to claim 2, wherein the pyrogenic silica particles are in the form of aggregates, said pyrogenic silica particles having a mean interparticular distance therebetween of between 0.2 and 0.7 μm, said aggregates having a maximum distance between two silica aggregates of ≦3 μm.